The present invention relates to a device for the electrophoresis separation of material such as proteins, protein subunits and nucleic acids. The device is used as the second separation in a two-dimensional separation system which begins with the isoelectric separation of species along a thin, elongated or spaghetti-like gel medium. In the original separation proteins ammino acids or other specimen material migrate, usually downwardly, to a previously established pH point within the gel at which the species of sample is electrically neutral, that is to its isoelectric point. Separation of these types are quite well known and when combined with a second dimension electrophoresis separation, the highest resolution of protein and protein subunits thus far developed can be achieved. In the second electrophoresis separation sample species migrate through a gel acting as a sieve to a point determined by their molecular weight.
The initial isoelectric separation is performed in a known manner. An isoelectric focusing gel of, for instance, acrylamide with catalyst, focusing compounds and crosslinking agents is formed and subjected to a prefocusing electrical potential between an alkali and an acid buffer solution, e.g., NaOH and H.sub.3 PO.sub.4. This establishes a pH gradient along the spaghetti-like isoelectric gel. The sample material is applied into the top of the gel containment tube and permitted to migrate under the influence of an electrical potential between the upper and lower buffer solutions. After a period of about 20 hours, the various sample species will have migrated to isoelectric points of neutral charge. The samples can then be removed from their containment tubes in preparation for a second dimensional electrophoresis separation.
The separation in the second dimension is performed by a sodium dodecyl sulfate electrophoresis within a two-dimensional acrylamide gel. Gel compositions are well known and include polymerization as well as cross-linking agents along with a gel buffer. Gels of this type have previously been assembled manually between glass plates with laboratory clamping devices and subjected to electric current between separate upper and lower buffer soluations. Such an apparatus and procedure is sufficient for performing occasional electrophoresis separations of protein specimens but is quite cumbersome and time consuming when a large number of samples must be run, as in genetic screening surveys and clinical diagnosis applications. The prior art devices for electrophoresis separations have been limited to one or at most two slab-gel media for sample resolution. These devices quite often leak buffer solution at gasketed seals where the slab-gel holders passed from the upper buffer solution container. Because of these limitations only a few slab gels could be subjected to electrophoresis at one time and substantial amounts of attention have been required by laboratory attendants.